The Frost Line Outer Defence Base Network, is endangered by the Mysterons when they destroy a maintenance truck, murdering it's engineer/driver in the process, as a cover to infiltrate the defence bases sited in Northern Canada, where the Mysteronised engineer intends to proceed in removing all oxygen from the bases' self-contained atmosphere.

With bases' ""Red Deer"" and ""Carriboo"" already taken down, the next base in the ring, ""Big Bear"", is the Mysterons' final target, but if the base is attacked also, the commander-in-chief of the defence network plans to commence a vengeful missile strike on Mars, where the main Mysteron complexes are established.

Colonel White desperately wants to prevent this from happening, and so, he assigns Lieutenant Green to his first off-base, ""in-the-field"" assignment, along with Captain Scarlet, to evaluate just how the bases are being cut off, and stop the maintenance engineer from triggering off a global disaster.

A newly produced core reactor is being transported to the Manicougan Power Complex, which is near enough found near the Atlantic Seaboard of North America, which the Mysterons have announced that they will submit a ""heavy blow to the prestige of the world.""

While conducting security checks within the designated area, it becomes aware that a missing, off-route Transporter 43, which has already inadvertently crashed over the edge of a demolished bridge, thanks to Captain Black's deliberate diversion of the planned route, is what the Mysterons are using to smuggle the reactor.

With the core reactor already being aerially ferried in a shipping helicopter, and with the controller at the Expo 2068 construction site looking down at the barrel of Captain Black's hand-gun, Spectrum are back to square one before they can investigate the reactor situation.

It becomes apparent however, that the copter's target is the Expo 2068 site, and evidence confirms that the thermal safety valve has been remo

An SKR-4 recovery vehicle is sent by the Euro-Space Tracker Station to destroy a live rocket, containing a malfunctioning destruct system, but ends being blown out of orbit and completely destroyed, when it collides with a considerably large meteorite.

Re-produced and controlled by the Mysterons, it becomes the bombing weapon, which will accomplish the forces' newest target: the Najama Complex, a vital colossal desalination plant, situated by the foothills of the Andes mountains. Its purpose is to process seawater from the Pacific Ocean, and irrigate the interior, and without it, hundreds of square miles would regress to waste land.

The complex is automated and requires very few personnel to administer the process, however it consists of vulnerable tanks, each containing liquid oxygen which would turn the whole valley into a ""blazing inferno"" if attacked with strong force.

While the complex personnel are evacuated, Captains Scarlet, Blue, Magenta and Ochre are sent to set-up surveillan